Treating surfaces of workpieces with abrasives



1947- K. H. BARNES 2,429,742 TREATING SURFACES 0F woaxPIEcBs IITHABRASIVBS Filed Oct. 12, 1944 2 Shoots-Shoot. 1

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I INVENTOR.

Oct. 28, 1947. K. H. B-ARNES TREATING SURFACES OF 'ORKPIECBS WITHABRASIVES med Oct. 12, 1944 2 Sheets-Sheet 2 FIO.

Y INVENTOR.

#aBmMM M /(M m ATTOQ I'Y Patented Oct. '28, 1947 TREATING SURFACES OFWORKPIECES WITH ABRASIVES I Kenneth H. Barnes, Mishawaka, Ind., assignorto American Wheelabrator & Equipment Corporation, a corporation ofDelaware Application October 12, 1944, Serial No. 558,425 (01. 51-9) 2Claims. 1 This invention relates to a method and device for thetreatment of surfaces of work pieces.

The invention provides a method and device for treating a surface toproduce a diffused smooth appearance, for removing impurities from asurface without injury to the surface or alteration of close surfacetolerances, for applying a finish to machined surfaces to increase theirlubricant. retaining ability, for increasing the fatigue life of thetreated parts and many other purposes.

According to theinvention a mixture, emulsion colloid, or suspension ofa finely divided abrasive and a liquid is prepared and is fed onto theblades of a centrifugal throwing wheel driven at high speed. Thebladesof the throwing wheel break up the stream of the mixture, emulsioncolloid, or suspension into small particles, each particle consisting ofliquid with abrasive suspended therein. The broken-up particles areaccelerated directly by the wheel and are projected at high velocity ina fan-shape blast without the aid of a carrying or enveloping airjet orliquid jet, and strike the surface of the work piece where they performthe desired surface treating action. The stream of particles dischargedfrom the centrifugal throwing wheel covers a large area of impact. Thesurface treating action of the particles is substantially uniformthroughout that area, insuring an even treatment of parts at all pointswithin a large area without formation of spots or focuses as arecommonly formed where air jets or liquid jets are employed forprojecting abrasive.

Work pieces to be treated may either remain fixed within the projectedstream of particles for a predetermined period of time, or may be movedthrough the stream by suitable means, such as a conveyer belt, aturntable, a chain; or the like,

Various kinds of abrasives and liquids may be employed. The abrasive maybe organic matter, such as pulverized husks or shells, or may beinorganic matter, such as emery, pumice, marble dust, silicon carbideand similar material and may vary in fineness from relatively coarseparticles to extremely fine powder of the order of 2500 mesh. The liquidmay be water or a nonoxidizing or corrosion retarding liquid such askerosene, light oils, carbon tetrachloride, trichlorethylene or otherliquids. The selection of the liquids is determined according to thematerials treated and the particular action desired. For example, it isoften advantageous to employ a liquid which is a solvent of impuritiesto be removed from the surface of the material.

The invention produces economically and at a 7 high rate of production,surface conditions which are not obtainable in any other way. Forexample, a velvety-smooth surface of extremely fine and onlymicroscopically perceptible grain may be produced on aluminum partswithout change of very close tolerances of the treated work piece.Aircraft engine parts, such as pistons, may be cleaned economicallyaccording to this method without wear or change in the dimensions of thetreated parts.

These and other features, advantages, and objects will appear more fullyfrom the detailed description which follows, accompanied by drawingsshowing for the purpose of illustration, a machine for practicing thisinvention.

The invention also consists in certain new and original features ofconstruction, combination of parts, and steps of procedure, ashereinafter set forth and claimed.

Although the novel features, which are believed to be characteristic ofthis invention, will be particularly pointed out in the claims appendedhereto, the invention itself, its objects and advantages, and the mannerin which it may be carried out may be better understood by referring tothe following detailed description taken in connection with theaccompanying drawings forming a part thereof in which- Fig. l is a frontelevation, partly in section of a machine for practicing this invention;

Fig. 2 is the side elevation, partly in section,

of a centrifugal throwing wheel of the machine, shown in Fig. 1 and Fig.3 is an elevation view of the rotor of the throwing wheel, shown in Fig.2, a section being taken on line 3-3 of Fig. 2.

The machine, shown in Fig. 1, comprises a cabinet l0 resting on asuitable base I l. A chamber l2 on the top of the cabinet ID houses acentrifugal throwing wheel 13 accessible through a cover l4 hinged atIS. The bottom of the'cabinet Ill may befunnel-shaped as shown at l6 andopens into a tank l1.

The cabinet Ill contains suitable means for supporting work pieces, suchas a turntabl l8 accessible through a door l9.

The turntable I 8 has a central shaft 20 driven by suitable means.

The tank I! contains a charge of a mixture 2| consisting of a liquid anda finely divided abrasive. The abrasive is maintained in suspension inthe liquid by a paddle wheel 22 on a through a conduit 25 equipped witha valve 28 for controlling the amount of mixture fed to the wheel l3.

Details of the centrifugal throwing wheel l3 are shown in Figs. 2 and 3.The wheel comprises a rotor'2l built up of parallel face plates, 28 and29, held together by connecting posts for spacers 30. The face plateshave radially extending grooves 3! adapted to receiv throwing blades 32held in place by set screws 33. The rotor 21 has a hub 34 mounted on adrive shaft 35 supported in a bearing 36. The drive shaft 35 isconnected to a suitable source of motive power, such as an electricmotor, capable of driving the wheel at high speeds.

The inner ends of the throwing blades 32 are tapered as at 31, anddefine a central space 38 into which a tubular discharge cage 39extends. The discharge cage isrotatably supported on a bracket 40. Theinterior space of the cage 39 communicates with the pressure duct 25which leads to a coupling 4| in the bracket 40. The control cage has adischarge port 42 in its periphery through which liquid and abrasivmixture is discharged in a predetermined direction against the innerends of the throwing blades 32.

The direction of discharge from the wheel may be controlled byadjustment of the clock-dial position of the discharge port 42 of thecage 39. The adjusting mechanism comprises a hand wheel 43 on a shaft44. The shaft 44 is mounted in a bearing 45 and carries at its outer enda spur gear 46 meshing with a further gear 41 integral with the hollowdischarge cage 39. A rotation of the hand wheel 43 causes a rotation ofthe discharge cage 39 relatively to the supporting bracket 40 and anadjustment of the direction in which liquid mixture is issued throughthe discharge port 42 against the inner ends of the blades 32 of thewheel I 3.

Driven at high speeds and supplied with a mixture of abrasive andliquid, the throwing wheel l3 discharges a fan-shaped blast 48 ofparticles ordroplets (see Fig. 1) against the turntable carrying theparts to be treated.

The operation of the device is as follows:

The tank I! of the machine is filled with a mixture of a suitable liquidand a finely divided abrasive. Parts to be treated are placed on theturntable l8. The centrifugal throwing wheel I3 is brought up tooperating speed and liquid mixture is admitted to the wheel by openingthe valve 26. The paddle wheel 22 agitates the abrasive and liquidmixture, so that the mixture maintains the character of a uniformsuspension. 1

The turntable 18 moves the parts to be treated slowly through thefan-shaped blast 48 discharged from the centrifugal throwing wheel. Thesurface treatment may be interrupted simply 4 by turning on the supplyof abrasive and liquid mixture at the supply valve 28, whereupon-theparts on the turntable may be removed.

The rotation of the turntable may also be interrupted at will in orderto discharge mixture against the parts while the parts are at rest.

The surface of the treated parts is comparable, in appearance and inmechanical properties to a honed surface. Impurities are removed withoutchange in the close tolerance of the treated parts. This is a particularfeature in reconditioning ma.- chine or engine parts, such as parts ofaircraft engines.

The method is very economical and requires only a fraction of the timerequired for conventional honing.

Another feature of the invention is the uniform action of the blast overa large area, as distinct from methods and machines operating on theair-jet or liquid-jet principle, where the jets usually leave anobjectionable track pattern on the treated surfaces.

A further feature of the invention is the unusually favorable ratio ofamount of mixture discharged per unit of power consumed. The powerrequired for discharging a given amount of mixture according to thisinvention is only a very small fraction of the power required in methodsemploying an air blast for accelerating. the particles of the mixture.

A further feature of the invention is the elimination of objectionablemoving air masses which tend to form a shielding film, or cushion, onthe surface to be treated through which the abrasive and liquidparticles have to be driven. The result is a more eflicient treatment ofthe surface for a given amount of mixture discharged thereagainst.

It has been found that treatment of machine parts according to theinvention increases fatigue life of the part considerably. This isprobably due to the elimination and rounding out of sharp marks andcrevices which, although only of microscopic magnitude, are found inpractically all machined parts.

Obviously the advantages of the invention are not limited to thespecific examples given, nor is the method limited to the use of theparticular machine hereinbefore described. Various modifications,additions, omissions and substitutions may be made by persons skilled inthe art without departure from the spirit and the teaching of thisinvention.

What is claimed is:

1. The method of surface treating, utilizing a centrifugal throwingwheel, which comprises forming a slurry in which finely divided solidblast particles are suspended in a carrying liquid, directionallydischarging under pressure a stream of said slurry at a substantialvelocity onto the inner ends of substantially radial blades of thecentrifugal throwing wheel adjacent its axis, rotating said wheel toaccelerate centrifugally the slurry received by the blades and to throwit as a controlled directional stream of uniformly dispersed liquid andsolid mixture.

2. In 'a system for directionally throwing a slurry in which solidparticles are-homogeneously suspended in a carrying liquid, a blastingwheel for directionally projecting the slurry, said wheel comprising acentral portion, means for rotating the wheel, a plurality of bl desextending from said central portion to the o ter'periphery of the wheel,a stationary closed chamber within said central portion, said chamberhaving a discharge REFERENCES 'crrEn The following references are ofrecord in the file of this patent:

UNITED STATES PATENTS Number Name Date Beeg Feb. 11, 1896 Perkins Aug.28, 1934 Fritsche June 19, 1935 Minich Apr. 20, 1937 Gartner Sept. 9,1941 Wieland Jan. 9, 1945 Grochoil Dec. 10, 1940 Hitchcock Mar. 8, 1927Burroughs June 15, 1937 Smith May 12, 1936 Tirrell Oct. 17, 1939

